mm/util.c

   1 #include <linux/mm.h>
   2 #include <linux/slab.h>
   3 #include <linux/string.h>
   4 #include <linux/module.h>
   5 #include <linux/err.h>
   6 #include <linux/sched.h>
   7 #include <asm/uaccess.h>
   8
   9 #define CREATE_TRACE_POINTS
  10 #include <trace/events/kmem.h>
  11
  12 /**
  13  * kstrdup - allocate space for and copy an existing string
  14  * @s: the string to duplicate
  15  * @gfp: the GFP mask used in the kmalloc() call when allocating memory
  16  */
  17 char *kstrdup(const char *s, gfp_t gfp)
  18 {
  19         size_t len;
  20         char *buf;
  21
  22         if (!s)
  23                 return NULL;
  24
  25         len = strlen(s) + 1;
  26         buf = kmalloc_track_caller(len, gfp);
  27         if (buf)
  28                 memcpy(buf, s, len);
  29         return buf;
  30 }
  31 EXPORT_SYMBOL(kstrdup);
  32
  33 /**
  34  * kstrndup - allocate space for and copy an existing string
  35  * @s: the string to duplicate
  36  * @max: read at most @max chars from @s
  37  * @gfp: the GFP mask used in the kmalloc() call when allocating memory
  38  */
  39 char *kstrndup(const char *s, size_t max, gfp_t gfp)
  40 {
  41         size_t len;
  42         char *buf;
  43
  44         if (!s)
  45                 return NULL;
  46
  47         len = strnlen(s, max);
  48         buf = kmalloc_track_caller(len+1, gfp);
  49         if (buf) {
  50                 memcpy(buf, s, len);
  51                 buf[len] = '\0';
  52         }
  53         return buf;
  54 }
  55 EXPORT_SYMBOL(kstrndup);
  56
  57 /**
  58  * kmemdup - duplicate region of memory
  59  *
  60  * @src: memory region to duplicate
  61  * @len: memory region length
  62  * @gfp: GFP mask to use
  63  */
  64 void *kmemdup(const void *src, size_t len, gfp_t gfp)
  65 {
  66         void *p;
  67
  68         p = kmalloc_track_caller(len, gfp);
  69         if (p)
  70                 memcpy(p, src, len);
  71         return p;
  72 }
  73 EXPORT_SYMBOL(kmemdup);
  74
  75 /**
  76  * memdup_user - duplicate memory region from user space
  77  *
  78  * @src: source address in user space
  79  * @len: number of bytes to copy
  80  *
  81  * Returns an ERR_PTR() on failure.
  82  */
  83 void *memdup_user(const void __user *src, size_t len)
  84 {
  85         void *p;
  86
  87         /*
  88          * Always use GFP_KERNEL, since copy_from_user() can sleep and
  89          * cause pagefault, which makes it pointless to use GFP_NOFS
  90          * or GFP_ATOMIC.
  91          */
  92         p = kmalloc_track_caller(len, GFP_KERNEL);
  93         if (!p)
  94                 return ERR_PTR(-ENOMEM);
  95
  96         if (copy_from_user(p, src, len)) {
  97                 kfree(p);
  98                 return ERR_PTR(-EFAULT);
  99         }
 100
 101         return p;
 102 }
 103 EXPORT_SYMBOL(memdup_user);
 104
 105 /**
 106  * __krealloc - like krealloc() but don't free @p.
 107  * @p: object to reallocate memory for.
 108  * @new_size: how many bytes of memory are required.
 109  * @flags: the type of memory to allocate.
 110  *
 111  * This function is like krealloc() except it never frees the originally
 112  * allocated buffer. Use this if you don't want to free the buffer immediately
 113  * like, for example, with RCU.
 114  */
 115 void *__krealloc(const void *p, size_t new_size, gfp_t flags)
 116 {
 117         void *ret;
 118         size_t ks = 0;
 119
 120         if (unlikely(!new_size))
 121                 return ZERO_SIZE_PTR;
 122
 123         if (p)
 124                 ks = ksize(p);
 125
 126         if (ks >= new_size)
 127                 return (void *)p;
 128
 129         ret = kmalloc_track_caller(new_size, flags);
 130         if (ret && p)
 131                 memcpy(ret, p, ks);
 132
 133         return ret;
 134 }
 135 EXPORT_SYMBOL(__krealloc);
 136
 137 /**
 138  * krealloc - reallocate memory. The contents will remain unchanged.
 139  * @p: object to reallocate memory for.
 140  * @new_size: how many bytes of memory are required.
 141  * @flags: the type of memory to allocate.
 142  *
 143  * The contents of the object pointed to are preserved up to the
 144  * lesser of the new and old sizes.  If @p is %NULL, krealloc()
 145  * behaves exactly like kmalloc().  If @size is 0 and @p is not a
 146  * %NULL pointer, the object pointed to is freed.
 147  */
 148 void *krealloc(const void *p, size_t new_size, gfp_t flags)
 149 {
 150         void *ret;
 151
 152         if (unlikely(!new_size)) {
 153                 kfree(p);
 154                 return ZERO_SIZE_PTR;
 155         }
 156
 157         ret = __krealloc(p, new_size, flags);
 158         if (ret && p != ret)
 159                 kfree(p);
 160
 161         return ret;
 162 }
 163 EXPORT_SYMBOL(krealloc);
 164
 165 /**
 166  * kzfree - like kfree but zero memory
 167  * @p: object to free memory of
 168  *
 169  * The memory of the object @p points to is zeroed before freed.
 170  * If @p is %NULL, kzfree() does nothing.
 171  *
 172  * Note: this function zeroes the whole allocated buffer which can be a good
 173  * deal bigger than the requested buffer size passed to kmalloc(). So be
 174  * careful when using this function in performance sensitive code.
 175  */
 176 void kzfree(const void *p)
 177 {
 178         size_t ks;
 179         void *mem = (void *)p;
 180
 181         if (unlikely(ZERO_OR_NULL_PTR(mem)))
 182                 return;
 183         ks = ksize(mem);
 184         memset(mem, 0, ks);
 185         kfree(mem);
 186 }
 187 EXPORT_SYMBOL(kzfree);
 188
 189 /*
 190  * strndup_user - duplicate an existing string from user space
 191  * @s: The string to duplicate
 192  * @n: Maximum number of bytes to copy, including the trailing NUL.
 193  */
 194 char *strndup_user(const char __user *s, long n)
 195 {
 196         char *p;
 197         long length;
 198
 199         length = strnlen_user(s, n);
 200
 201         if (!length)
 202                 return ERR_PTR(-EFAULT);
 203
 204         if (length > n)
 205                 return ERR_PTR(-EINVAL);
 206
 207         p = kmalloc(length, GFP_KERNEL);
 208
 209         if (!p)
 210                 return ERR_PTR(-ENOMEM);
 211
 212         if (copy_from_user(p, s, length)) {
 213                 kfree(p);
 214                 return ERR_PTR(-EFAULT);
 215         }
 216
 217         p[length - 1] = '\0';
 218
 219         return p;
 220 }
 221 EXPORT_SYMBOL(strndup_user);
 222
 223 #ifndef HAVE_ARCH_PICK_MMAP_LAYOUT
 224 void arch_pick_mmap_layout(struct mm_struct *mm)
 225 {
 226         mm->mmap_base = TASK_UNMAPPED_BASE;
 227         mm->get_unmapped_area = arch_get_unmapped_area;
 228         mm->unmap_area = arch_unmap_area;
 229 }
 230 #endif
 231
 232 /**
 233  * get_user_pages_fast() - pin user pages in memory
 234  * @start:      starting user address
 235  * @nr_pages:   number of pages from start to pin
 236  * @write:      whether pages will be written to
 237  * @pages:      array that receives pointers to the pages pinned.
 238  *              Should be at least nr_pages long.
 239  *
 240  * Returns number of pages pinned. This may be fewer than the number
 241  * requested. If nr_pages is 0 or negative, returns 0. If no pages
 242  * were pinned, returns -errno.
 243  *
 244  * get_user_pages_fast provides equivalent functionality to get_user_pages,
 245  * operating on current and current->mm, with force=0 and vma=NULL. However
 246  * unlike get_user_pages, it must be called without mmap_sem held.
 247  *
 248  * get_user_pages_fast may take mmap_sem and page table locks, so no
 249  * assumptions can be made about lack of locking. get_user_pages_fast is to be
 250  * implemented in a way that is advantageous (vs get_user_pages()) when the
 251  * user memory area is already faulted in and present in ptes. However if the
 252  * pages have to be faulted in, it may turn out to be slightly slower so
 253  * callers need to carefully consider what to use. On many architectures,
 254  * get_user_pages_fast simply falls back to get_user_pages.
 255  */
 256 int __attribute__((weak)) get_user_pages_fast(unsigned long start,
 257                                 int nr_pages, int write, struct page **pages)
 258 {
 259         struct mm_struct *mm = current->mm;
 260         int ret;
 261
 262         down_read(&mm->mmap_sem);
 263         ret = get_user_pages(current, mm, start, nr_pages,
 264                                         write, 0, pages, NULL);
 265         up_read(&mm->mmap_sem);
 266
 267         return ret;
 268 }
 269 EXPORT_SYMBOL_GPL(get_user_pages_fast);
 270
 271 /* Tracepoints definitions. */
 272 EXPORT_TRACEPOINT_SYMBOL(kmalloc);
 273 EXPORT_TRACEPOINT_SYMBOL(kmem_cache_alloc);
 274 EXPORT_TRACEPOINT_SYMBOL(kmalloc_node);
 275 EXPORT_TRACEPOINT_SYMBOL(kmem_cache_alloc_node);
 276 EXPORT_TRACEPOINT_SYMBOL(kfree);
 277 EXPORT_TRACEPOINT_SYMBOL(kmem_cache_free);